It is known to apply coatings of all sorts of metal oxides, in particular of tin dioxide, to glass containers in order to improve their resistance to impact and abrasion. This tin dioxide coating acts as a primer for the so-called cold end coating applied after the annealing process.
Customarily, tin compounds are brought into contact with the hot glass surface in vapor or spray form in the so called hot end coating, a thin tin dioxide coating being produced pyrolytically. On account of their physical properties, such as water solubility, vaporizability and the like, and of their low toxicity, monoorganotin trichlorides are, in particular, employed for this purpose (DE-C-25 41 710).
Depending on the purity and quality of the products, however, it has been shown in the processing of these compounds that due to the occurrence of solid particles, in particular after long storage, significant trouble can occur with the glass coating process. significant trouble can occur with the glass coating process.
According to EP-A-0 132 024, to avoid the occurrence of solid particles, dopants of all sorts of types, in particular alcohols, are added to the monoalkyltin trihalides.
A further problem which occurs with monobutyltin trichloride after long storage is darkening, which can lead at its most pronounced to a dark brown coloration. This dark coloration of the product can likewise significantly adversely affect the working process, in particular in measuring and metering operations. Furthermore, with monobutyltin trichloride visible crystallizations very rapidly occur under the influence of moisture; on longer action, presumably caused by hydrate formation, the formation of a liquid multiphase system can even occur.